Intro exposure

Exposure: The amount of light falling on light
sensitive material.
Introduction to Exposure
Exposure

Exposure: The amount of light falling on light
sensitive material.
Proper Exposure: The CORRECT amount of
light to properly expose light sensitive
material, determined by four factors:
illuminance, shutter speed, aperture & ISO
Exposure

1) Illuminance
2) Shutter speed
3) Aperture
4) ISO
Four Factors

1) Illuminance: The strength of light falling on
a given area
2) Shutter speed: The measured amount of
time through which light strikes the film or chip
3) Aperture: The size of lens opening through
which light passes
4) ISO: A numerical rating that describes the
sensitivity to light of film or of a digital chip
Four Factors

1) Illuminance: Determined by the Sun or
other light source
2) Shutter speed: Determined by YOU
through camera control
3) Aperture: Determined by YOU through
camera control
4) ISO: Determined by YOU through
camera control
Four Factors

The factor that you typically have no
control over. For example, direct sunlight,
standing in open shade, the light of a
candle or the brightness during overcast
conditions.
1) Illuminance:
Four Factors

You can control the amount of light by
adding flash, moving you and/or your
subject, waiting for different weather.
1) Illuminance:
Four Factors

2) Shutter speed: Determined by YOU
through Camera Control
Four Factors

The camera control that opens and closes
the shutter to admit light into the camera
for a measured period of time. Those
periods of time are measured in fractions of
a second.
2) Shutter speed:
Four Factors

Should be thought of as the time or
duration and is measured in 1/3 stop
increments.
Four Factors
2) Shutter speed:

The numerical expression for shutter speed
is a fraction of a second and is twice as
much or half as much in WHOLE stop
increments.
Four Factors
2) Shutter speed:

A Complete List of Shutter Speeds in 1/3 Stop Increments
Four Factors
2) Shutter speed:

A stop is a change in exposure or illumination
by a factor of two. One stop more exposure
doubles the light reaching the film or chip.
One stop less exposure halves the amount of
light reaching the film or chip.

The amount of light is ALSO measured in
twice as much or half as much in WHOLE
stop increments.
Four Factors
2) Shutter speed:

1 sec 1/2
1/2 1/4
1/4 1/8
1/8 1/15
1/15 1/30
1/30 1/60
1/60 1/125
1/125 1/250
1/250 1/500
A one stop difference
Four Factors
2) Shutter speed:

It Stands To Reason Then ...
From 1/8000 .................... To 1/4000
is one full stop more light.
1/8000 .... is twice as fast as .... 1/4000
and lets in half as much light.
1/4000 .... is half as fast as .... 1/8000
and lets in twice as much light.
Four Factors
2) Shutter speed:

1/4000............... is twice as fast as ................1/2000
1/2000............... is twice as fast as ................1/1000
1/1000................ is twice as fast as .................1/500
1/500................. is twice as fast as ..................1/250
1/250................. is twice as fast as ..................1/125
1/125.................. is twice as fast as ...................1/60
Because Shutter Speeds are listed as fractions of a
second they relate to one another in this “twice as
much” or “half as much” way at full stop intervals.
Four Factors
2) Shutter speed:

3) Aperture: Determined by YOU through
Camera Control
Four Factors

The camera control that determines the
amount of light that passes through the
lens. That amount of light is measured in
fractions of focal length in 1/3 stop
increments.
3) Aperture:
Four Factors

Let’s Take A Look At A Complete List Of Apertures...
©Photography: Eighth Edition
3) Aperture:
Four Factors

The ‘f’ number represents the amount of
light and is figured by the size of the
opening (aperture) divided by the focal
length of the lens.
3) Aperture:
Four Factors

Think of the numerical expression, ‘f’ as a
fraction.
f/16 or f/2.8
The larger the number, the smaller the
opening.
3) Aperture:
Four Factors

No matter what focal length lens, the ‘f’
representing aperture lets in the same
amount of light.
3) Aperture:
Four Factors

For example, f/2 on a 50 mm lens lets in
the same amount of light as f/2 on a
300mm lens.
Even though the actual size of the opening
is different for these two lenses, the amount
of light is the same.
3) Aperture:
Four Factors

Good news is the amount of light is
measured as a factor of two at WHOLE
stop increments.
3) Aperture:
Four Factors

Good news is the amount of light is
measured as a factor of two at WHOLE
stop increments. The bad news is the
numerical expression at WHOLE stop
increments is at a factor of 1.4
3) Aperture:
Four Factors

Let’s Take A Look At A Complete List Of Apertures...
The bold printed numbers are one stop increments!
In what way do you think apertures relate to one another?
3) Aperture:
Four Factors

Aperture controls, in one stop increments,
work in the “half as much” or “twice as
much” manner as well.
So We Begin To See Then ...
3) Aperture:
Four Factors

Even though we haven’t gotten to the fourth
factor of exposure, you have to understand
that the reciprocal relationship between
aperture and shutter speed provides a
balance with amount of light to provide the
ONE CORRECT EXPOSURE.
3) Aperture:
Four Factors

So How Do Shutter Speed and Aperture Work
Together ?
The rule of thumb is this;
For proper exposure
If we choose a faster shutter speed (which lets in less
light,) we have to choose an aperture (that lets in more
light) and vise versa.
3) Aperture:
Four Factors

4) ISO: Determined by YOU through
Camera Control
Four Factors

The camera control that determines the
sensitivity of film and digital chip. It is
represented by a numerical value in 1/3
stop increments.
4) ISO:
Four Factors

Let’s Take A Look At A Complete List Of ISO’s...
The bold printed numbers are one stop increments!
In what way do you think they relate to one another?
4) ISO:
Four Factors

The numerical expression in WHOLE stop
increments is measured in a factor of two
(twice or half as much).
4) ISO:
Four Factors

The sensitivity to light in WHOLE stop
increments is measured in a factor of two
(twice or half as much).
4) ISO:
Four Factors

If ISO 400 is “Twice As Much” as ISO 200,
at ISO 400 the chip in the camera is “Twice
As Sensitive” as the same chip at ISO 200.

It stands to reason then, that a shutter speed of
400 is twice as fast as a shutter speed of 200.

So, with twice the chip sensitivity, it only
requires the shutter to be open half as
long to produce the exact same
exposure.
It stands to reason then, that a shutter speed of
400 is twice as fast as a shutter speed of 200.

ISO 400 ISO 200
So, side by side, it’s clear to see that the exposure is the same if
illumination is a constant no matter what the ISO. If we learn to
understand how ISOs, shutter speeds, and f-stops relate, we will then be
fluent in understanding the basics of photography.
©Rick Ricman

In the world of camera controls
“Half as Much”
and
“Twice as Much”
inherently applies in one stop increments.
Exposure

1/200 @ f/16
is the same as
1/ ? @ f/5.6
Let’s try a problem...
Exposure

f/2.8 f/4.0 f/5.6 f/8.0 f/11 f16
Returning to the f Stop scale
f/5.6 is 3 stops more light than f/16.
Therefore,
our shutter speed has to be 3 stops faster.
Exposure

100 200 400 800 1600
On The Shutter Speed Scale
Which number is 3 stops faster than
200 ?
Exposure

1/200 @ f/16
is the same as
1/1600 @ f/5.6
So the answer to our problem is;
Exposure

To maintain equivalent exposures, when we increase our shutter speed we must also decrease
our f- stop (aperture) by the same amount. Conversely, if we decrease our shutter speed we
must then increase our f-stop (aperture) by the same amount.
©Rick Ricman
1/1600 @ f/5.6 1/200 @ f/16

Intro exposure

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Intro exposure